The present invention relates to an oil pan structure for an internal combustion engine, and more specifically to an oil pan structure having a baffle plate.
In general, an oil pan structure has a deep oil storage section for storing a lubricating oil and a shallow oil collecting section for collecting the lubricating oil falling in the crankcase and directing the lubricating oil into the deep section. An oil pump driven by the crankshaft sucks the oil through an oil strainer from the deep section, and distributes the lubricating oil to various parts of the engine for lubrication.
The crankshaft and connecting rods rotate at high speeds closely over the oil pan. In order to prevent undesired collision between an engine rotating part and the lubrication oil, the shallow section of the oil pan is required to guide the lubricating oil promptly to the deep section. An oil pan structure disclosed in a Japanese Patent Provisional Publication No. 62(1987)-247158 has one or more rib-like flow regulating plates projecting upwards from the bottom of the shallow section and extending along a longitudinal direction of the engine to guide the lubricating oil smoothly into the deep oil storage section.
In some examples, a baffle plate of sheet metal extends over the shallow section to prevent the lubricating oil from swinging upward during a cornering operation of a vehicle and bumping against a rotating part. The baffle plate is formed with a plurality of oil collecting slit-shaped holes for allowing the lubricating oil to flow into a lower space in the shallow section under the baffle plate.
However, the oil collecting holes and the flow regulating plates are located separately, and the conventional oil pan structure is limited in rate of discharging the lubricating oil from the upper side of the baffle plate to the lower side. Specifically in a high engine speed range in which a large quantity of the oil is circulated, the limited drainage from the baffle plate tends to cause the oil to stay long on the baffle plate and to increase the possibility of collision between an engine rotating part and the oil on the baffle plate. The draining speed can be improved by increasing the opening size of the oil collecting holes. However, this tends to impair the ability to perform the required function of the baffle plate.